Sander



April 16, 1940. c A. CAMPBELL SANDER Filed 001;. 6, 1938 3 Sheets-Sheet 1 4 3 M EEO My PZOMM hi-EN m Q Smentor day ANNE;

Pzoum .rIoE V L Ill/II ill] " U III! April 0- c. CAMPBELL 2,196,978

SANDER Filed Oct. 6, 1938 3 Sheet-Sheet 2 (Ittornegs C- A. CAMPBELL April 16, 19 0,

SANDER Filed Oct. 6, 1938 3 Sheets-Sheet 3 Push d Apr.'"1 6 ,1940

" isANnEn' Charles}. Campbell, Wat'er town, N; Y. ,"assignor l to'The New York.Air Brakejconrpany, a. 001'.-

. ,poration'of New"Jersey Applicationoctober' fi, 193a, -.s'e.-a1 no; 233,679

This inventionrelates to' sanding devices for r high speed trains; and particularly to means for" shortening the interval between the actuation of the device which causes l sanding, and the actual initiation of a sanding operation at the rail.

Brobablythegreatest, cause of time lag isoccae sioned by location (-of thesand trap ata point remote-from'the point of sanddelivery. vIt has heretofore beenpropose'd to mount gravity sand boxes directly on the-truck and deliver the sand by-gravityto the rail in front of the wheelsbut' the necessary size of the sand box makes the" scheme 'undesirableev'en in'cars of olddesign,

and impracticable onzmodern high speed streamlined cars in which the bo llyi 10w on the trucks,

the 'four wl1eel, trucks q'oom-monly used are equip'pied'with four brake cylinders and. such comthere' islittleavailable space on the truck.

present invention solvesthe problem of short'p'ath' delivery bymounting on the trucksmall sand traps, each with a local sand storage chamber only 'largeenough to contain the charge of sand'for a single timed sanding operation.

This is'ie'asible because modern sanding devices commonly include'a timingdevice which causes them to deliver sand for the duration of an emergency stop. Such sanding systems also include additional manually operabledevices for sanding at will; butthe duration of such sanding operations is' n'o'rmally shorterthan the "duration of thetimed sanding above described. Consequently; a local storage chamber which will pro automatic timed operation will vide'for a single v meet the requirements'of the service.

To permit the use-10f these small local chambers, I mount a sand box'of substantial size; on the car body and provide flexible tubularjsupply connections fromthe'main sanding box to the local chamber's on the trucks. With these" is usedva' measuring'feed mechanism which', as an incident; to each sandingv Operation,- will supply,

from the. main sandbox to'each local. chamber, a charge of sand justsufiicientto' refill the local chambers. I 7

- scheme is workable des'pitethe limited space. available on high speed streamlined cars.

' It can be arranged tosand; in front of 'the leading what by the factthat such trains operate at high speed in one direction Only; For this, reason' sanding for aIbacking, except. on, the propelling unit, is amatter of minor importance.

of .the truck. The problem is simplifiedsomefwheels of-the "truck. only or in front of all wheels application. I g

I I shown; plicatedspring plankand linkmechanism. that. u u

11; Claims. (01. ser s) *The' invention makes use of an adaptation of the intercepting valve mechanism described and claimed in -the application of Campbell and Safford, Serial No.-.149,193, filed June 21, 1937. Cons'equently, no broad ;claim' to this intercepting valve mechanism per se is made in the present Systems of the type above outlined are capable of embodiment in specifically different forms The detailsvof each installation depend on structural aspects ofthe train to which-it is applied.

Hencein this specification the desc'ription of the invention will be basedon a general schematic showing sufilcient to permit explanation of the operative principles of the invention without eveniniplied limitation to the specific arrangement Itis simpler to describe sanding for the front wheels oi the truck only. Since" the provision of additional means for sandingother wheels on the sametruck involves mere duplication of trap and local chamber units, only mechanical skill is required to adapt the scheme to more wheels or even'all wheels on the train. Similarly, it is immaterial whether the train be of the articulated type or of the type in which each car is complete in'itself, orinvolve some combination of these two schemes as in the case of certain streamlined trains operating in the West; These diiferences t affect the location of the} main sand boxes, the number of'units, and similardetailslbut the in-.

vention in its basic principles'is applicable with onlyslight variation to meet requirements imposed by" the particular construotionjof the train. T The invention will now be described with referehce to the accompanyingdrawings, in. which:

Fig. Lisa piping diagram of a system having a, motor 'car and vone trailer. Only two sand traps are. shown on each of the two cars, each car being fitted with a single sand box to supplysand to the 1 local chambers of each of thetwotraps on that car. The-purpose is to show a plurality of sandersj'with local reservoirs and still keep the number at a practicable minimum to simplify the description. A larger number of sanders would ordinarily be used and each would be, equipped with a local reservoir and with means for feeding'from the main sand box. In thisview pneumatic con-, trolls indicated on the motor car with electric point of speed of operation.

control on; the trailer, thetwo schemes being f approximate equivalents except from the stand- Fig. 2 is a diagrammatic section of the sander control mechanism carried on themotor car.

' Fig. 3 is a similar sectional diagram of the controlled mechanism carried on the motor car.

Note-By assembling Fig. 2 immediately above Fig. 3 a-complete diagram of the sanding appae ratus for the motor car corresponding to the lefthand portion of Fig. 1 is produced.

. Fig. 4 is a sectional view of the magnetvalve and piston ,operated valve controlled thereby which are mounted-on the trailer and usedfto operate thesande'r. The sand box,fsand traps,

and local chambers on the trailer are identical.

in structure with the showing in Fig. 3 I

Fig. 5 is a section on the line 5-,5 of, Fig. 3 and shows the construction of the measuring chainher where the sand box delivers tdtwosand trapa Fig. 6 is a horizontal sectionthroughf a"loc'al' sand chamber on the plane of the sand inlet. Y

Referring first to Fig. 1, 6' represents tansengil-i/zl neers brake valve assumed to have ansanding When the engi-fl port connected toHthe pipe n'eers brake valve is moved to emergency post'- tion'the sanding port admits air at main reservoir pressure to pipe 'I', and this is caused to operate the-sanding mechanism as hereinafter explained. 8 indicates-the bodyjof a sander valve which may be, brought'into action by the operation of the engineers brake valve as just described.- ,It may be caused to sand for a definite time interval by depressing the button 9, and may be caused to isand for any shorter periodby depressing. the" button II, sanding continuing while the button I I is held depressed.

The timing reservoir I2 tion ofsanding if the valve 3 is operated either by movement of theflengineers brake valve 6 to emergency position or by pressing thebutton ll, the duration of sanding being the same in either case. Anairreservoir it supplies air under pressure for the sanding operation. This may be the f I main reservoir of the brake system or any other suitable source of air under sufficient pressure.

The sander valve 8 is connected by the branch pipe is with "two devices for controllingv the sander. The first of these is a pneumatic relay I5 which in the example illustrated controls the supply of sanding air to the sander mechanismon the leading vehicle. The second of these devices is apressureoperated switch generally indicated by the numeral'l'fi and controlling a train circuit for causing sanding on the trailers.

Switch 86 comprises a piston ILnormally held down by a spring is and subject on its lower side to the pressure in pipe Hi. When the piston is forced up-by pressure developedin pipe M, a con tactor I9 closes a'sander circuit comprising wires 2!, 22,13, normally closed switch 26;asource of electric current typified by battery 25 through the actuating winding 26 of the magnet .valve indicated generally at-Zl. This magnet valve, when its Windingis excited, admits pressure fluid to1a piston-operated sander valve'generally indicated at 28, and opens the same admitting actuating air to the sanding units on the first'trailer. Where more than 'one'trailer isused, as is commonly the'case, the windings 26 ofthe magnet valves for the various trailers are connected in parallel betweeu-wires 'filand 23 so that 'allthe' magnet valves 27 operate simultaneously. 3,

. The sander valve 8 is manufactured in substan' tial accordance-withthe U; S. Patent to Campbell;

No. 2,035,533 issued March 31, 1936,- and is illustrated in s'ectionin Fig. 2. Since the structure-is known and is not here-claimed, a brieistateme'ntof its operation will sufiice. The pipe I leading from :the Engineers brake valve-' 6 suppIies air- 31* with" reservoir .12.

untilfthechol ze 3T hasbled reservoir I2 to such determines the dura-' above the piston 3 I and will force that piston" I downward'producing exactly the same efiect'that is produced by forcing the knob downward. E'It. causes'movement ofbalancedpiston valve 32 to itsllowermost position against the resistance of espring 33. In its uppermostposition mainreser p voir air supplied through the pipe-34 passes the reduced middle portion of valve 32 and flows thr ough- .the. pi e 35 tothe timing reservoirflL p is shifted by button 3 why piston (H; the reduced portion of the valve connects reservoir IZ- with t1 1e.-.'spacev above piston 3B'so' that valve- 32 is charging it tosupply pressure. When'th'e valve moved all the way down,blank ing suppl'y connec-t' tion "34* and c'onnejc'ting pipe It and exhaust choke tTlieTefiect of'such motion. thereforlis to develop;suificientdownward air pressure on pisten 36 to hold the valve in its lowermost position a lowpressure that spring; 33 canrestore the :valve cam its initial position, The parts-iare-so de-e Y signed that the valve sz will stayin its.lowermost position for a period slightly longer. than tithe: durationof an emergencyjstop'. 7 1

When thevalve isv restored to its uppermost v position; port I II is blankedand choke-31 immedii:

ately ventspiperI lg; It willgbe'understdOdthat .the eXistence of. substantial pressure in pipe ill causes sanding on the trailers bygclosing: the-gall sw itchl's'and causes sanding {on themotorcarlbyj opening-the pneumatic relay I5. I In .order to secure sanding at; will. whemthe. valve 32 is in its uppermost or ,norm'alipositiomapoppet valve 38 is provided. :This valveis une seated by the.,button II. against resistanceof'a p spring Iii-Land when opened,connectslthesupply; line 3d viathe reduced portion .ofthe valve i2.

with the. port 4 I' which leads tothe'connection I 4;,I

but not i th e o e th iSn6 C eiii quently, pressure will be developedin pipe I4-sol,

1 long as the buttonl I is held 'depressedand will be I dissipated "rapidly through chokef'3l when the;

button I I is released and the valve! 38- :elosedw The relay l5,'which" is shown in section in Fig.5 2, comprises a cylinder 42 in whic'h isa piston 43'. The pipe I4 communicates 'tvith' the space below piston 43;" The space above the pistonfcomm unir cates with the pipe which delivers sanding air Y. to' the sandingmeclianism, that is, to the mecha" 1 nism which delivers sand 'from the. sand b'oxzto. V

th -local reservoirs .on the traps and also. to the; air jejtsland intercepting valves'formingpartsofl the trapsgThe piston 43 has astemj 45, guided} at is and carrying a plu nger l l which is urged outward by the coil compression springflflhoused inthestem When the piston; 43"is forced up: W 113711115694 5 p ppetvalve 5D andgadmits to main freservoir'v air pressure ;which"actson*t 3 ling valvel'idj The double beat valve'ismiased as 701 stated by a coil compression spring; so*that{.

. normally the pipe bfiis vented toatmos'phere but Y when the winding 2E5 is-energized-,;the valve 531s closed and the -valve-blis: opened,-so thatair y from the supply reservoir coming byw'ay of. the 35s aicaovs train pipe 51 which is connected from vehicle to vehicle as indicated at 58'; is admitted through a branch pipe 59 to the pipe 56.

The 'pipe 56 is connected to the piston-operat- 1 ed valve generally indicated at 28 in Fig. 1 and shown in section in Fig. 4. Airip'ressure, when admitted, depresses the piston6l and opens the poppet valve 62 against the resistance of the.

function with two branches of pipe 44, which.

s, The arrangement above shown is such that if the engineers brake valve is movedto emergency position, or if the button 9 is depressed, the pipes 65 and 66 onthe motor car and the pipes 65a. and 66a on the trailer will be subjected continuously to supply pressure for a definite time period. 1 If the button H is depressed, the pipe named will be subjected tosupply pressure as long as the button is depressed. However, since the sand trap holds acharge of sand only sufficient to last for the duration of an. emergency stop, continuoussanding cannot last longer. Re-

consequently are designated on Fig. l as 65 and lease of button II will, however, cause prompt sand recharge.

Upon the termination of such a sanding operation and dissipation of pressure in the pipes 65 and 66, the sanding mechanism will automatically recharge itself and become almost instantaneously ready for an ensuing sanding operation. The operation of this part of the mechanismcan best be described with reference to Fi 3. I

Fig. 3fshows,simplythe unit on the leading car as clearly indicated in Fig. 1. This unit is duplicated on the single. trailer there shown and would be duplicated on any additional trailers in the train. The main sand box 61 for a'group of sand traps is intended to be mounted on any be clearly understood that a single sand box 61' can furnish sand to any reasonable number of sand traps. That is, it may supply sand to anyreasonable number of sanders on a single truck, or if the vcar has more than one truck, it may furnish sand to any desired number of sanders on the various trucks. In other words, the sand box 61 is simply a reservoir from which sand is forciblyfed to localsanding chambers associated with a plurality of sand traps.

The sand box 61 has a removable cover 69 clamped in place by a wing-nut as shown and provided with a breather filter H. The bottom of the sand box is provided with a jacket space 12 througlrwhich a heating fluid may be circulated by way of the pipe connections 16. Mounted ,below' the discharge opening 13 of the sand box 6'! isa body 'l l which houses the intercepting valve and the: measuring chambers. The structure of these measuring chambers is clearly indicated in ;Fig. 5;,in which there are two chamof sand. This unit comprises a supporting screen 1-5 bers l5 and 16 of equal volumeseparated' by a divider partition 11.

-Fig. 5 shows two chambers because Fig.' 3

shows-two sand traps. The number of chambers will correspond to the number of traps to be fed.

The discharge opening 13 communicates with the. measuring chambers 15 and 16 through a distensib-le tube. of rubber or like material indicated at 18 and sustained by a bushing 19which engages the upper and lower flanged ends of the tube andleaves the middle portion of the tube laterally unsustained by aifo-rding, the chamber orchannel 81 around the same. Mounted immediately below the lower end of the tube'lfi. and:

arranged to seat against gthe lower end thereof,- is the intercepting valve. This comprises a fixed tubular stem 82 with the distensible bulb 83 of rubber-like material over which'is mounted the inverted cup-shaped valve element 84. the bulb 83 is inflated, the. valve 84 seatson the lower end of the tube 18, which as stated is supported by the bushing 19. However, sand in the When tube 18, if it tends to arch and resist .upward flow, will simply spread the tube 18 into the space iiiv so that the valve 84 may close tightly. This is important as it not only prevents dribbling of the sand, but insures hermetic closing of the measuring chambers during the sand transferring operation.

- The pipe 66 leads to the chamber 85 with which the bore of stem 82 is in open communication, so that when pipe 66 is under pressure, the valve 84 is closed. Chamber 85 also communicates with the bores of two nozzles 66 which-are directed across the lower portions of the two measuring chambers 15 and 16 and discharging into ejector tubes 81, one in eachchamber, which are; indi vidually connected by pipes 88 and 89 withthe local sand chambers 9| which are associated with the respective sand traps 68.

I Thus, when the pipe 66 is not under pressure, the valve 84 is open, and sand flows down through thetube 18 and fills both the chambers 15 and 76 full of sand. When air under pressure is admitted to pipe 66, the valve 84 will close, isolating the measuring chambers from the sand box andthe nozzles 86 will begin to eject sand from the correspondin measuring chambers and deliver it to the corresponding local chambers 9| for the various sanders. I

' Itwill be helpful to observe at this point that the capacity of the measuring chambers 15 and 16 (there being one such chamber for each trap to be fed) corresponds with the capacity of the local sand chambers 9| to which they respectively deliver, and that the local sand chambers,

at the time such delivery starts, will be empty Each local sand chamber 9| is mounted on top ofthe corresponding sand trap 68 and has at its top a vent opening protected by a depending skirt92 whichdefines a centrifugal chamber into which the sand is projected tangentially, as indicated at 90. (Fig. 6). protected by a removably mounted sand-arrestingfilter and rubber protecting cap designed to The vent opening is further preventthe entrance of moisture and the escape y from the local chamber 9| into the bodyof they or perforated .platetiliiy a fabric filter 94';a second; screen or perforated plate 95'; .asperforatedtre taining spider 96, a 'cup-shapedrirubber-valve 'element 9'! havinga downward .extending peripheral flange, a washer 93, ando;aretaining. screw 99' which is. threaded vinto thehub of .'a.spider' HH cast integrally with the body'ofwthe chamber 9!.

The discharge opening. I [l2- :delivers LilItO iautub'e: I03 sustained by an insertltl i. The :parts: 103' and IM are structurallyandfunctionally similar. toithe parts T8 and-.m'already described? There is. :also an intercepting rvalve having-:astem 105,

bulbhead. I05, and valve lelement "I01; which arestructurally and functionally similar toparts 82, 83 'andtt already described.

The line -65 leads directly to the boreuofi thetubular stem I65, and since the pipes- 65 and "66 are subjected to pressure simultaneously," the valve ill! will close simultaneously with the 010- sure of the valve 84. Thus; between sanding-op erations the valve ifllpermits sand to flow freely trap 68. Chamber 9| is so dimensioned as to hold thecomplete charge of the sand trap so thatat the termination of a sanding operation when the valve lB-Topens; all the sand will flow from thesan der 9| into the trap 68.

At the commencement ofthe sandingoperation the valve H11 closes so that While sand is being fed from the measuringchambers 15, or was the case may be, into the corresponding chamber 9!,

that chamber is isolated from the sand trap. The

pipe 65 is'in free andconstant communication with the stirring nozzle Hi8 which discharges un-' der the baffle I69 and in a direction away'fr'om the crest HI over which sand must flow to enter the sand conducting pipe H2. This pipe] l2 terminates in a distensible rubber nozzle I i3 which is directed to the angle between the wheel and g the rail. A nozzle: l M} aligned with the'stem 1850f the intercepting valvesends a jet of air down the pipe lIZgand like the nozzle HEB-is in constantly free communication with the pipe 65.

It should be observed further that since the valve lll'l' seals air-tight; the trap. operates under high pressure.

It should also be observed that whenthepipe 65' first delivers pressure "fiuid'to the'trap, a cleanout blast is discharged at' I I 5*across the top of trap 68 and simultaneously through H6 to' the entrance-end of the pipe H2. Thepurpose-oi thisis to develop equal pressures above and below partition itd'so that the charge of sand will not be-bwn*out of the trap;

Thecle'an-out blast through openings H5 and lle is only temporary and is controlled by an intercepting diaphragm I ll which is urged against aseat '5 it by aspring E9 The seat H8 controls flow. to the passage 52! which leads to the'passages lifiand H6: From the pipe65 flow is by way ofa -port 522 to thespacearound the seat H3; Thefirsteffect is toover-powerthe spring IIQand force the diaphragm H1 back, buta:

chokeiflli leads air from the port- I22 "to the space behind the-diaphragm H'l so that afterasshorttimeinterval 'air pressures on the'diaphragm i ll equalize and spring H9 seals the diaphragm on the seat H8; Hence, the initial lastthrough passages HEand i 16 occurs only for 'a shorttime, determined by the relative capacity of-itheichoke I23 and the chamber behind' 'Ihe'location of the timing.

VaIVB'ZdiIiECtIY inv the trap. accelerates the delivery a of the clean-out blast and. hence; contributes :to

the diaphragm. i H.

rapidinitiation of :sanding;

' switch .24.

' The:generaltoperationrofthelsystemzhasaiready beenzdescribediand :a brief :summary 'will sufficezq Timed sanding .is: initiated by rnoving the-rent: gineers': brake I valve; 6 itofiemergency=positionxlor b'y-depressing; the button 9:- Sandingat will,flthat.

is; without the timing; feature, may be: brought aboutxby holding downathezbutton' l l and may-"bee had" as longas desired withibrief interruption to replenish theisan'dlinr the trapssirr theararea case that lsandihgifor; avery' long period iszasde-lv sired; On the leading car theiprreumaticmelayl i5 rputsthe1pipesr65 andnfifi underipressure:delive I ered: directlyirom the supply; reservoir; l3. 1 Oh thetrailervehicl'e; or vehicles, the pipesfitiarandz I BEazare supplied with airzfiionr the samersource: by the operation of the magnet valve 2'! and the piston-operated valve 2 2 8: Theduration off; air flOVV'u during timed sanding .on: the leading; car: and: onthe trailers is the same." Electriciactue.-

. ationiszfaster than pneumatic-actuationand-is.

therefore preferred; particularlygfor the trailers;

but pneumatic actuation is possible .and is shown: on the leading'car towhichit isvwell; adapted:

becausethe-distance is so short that pneumatic actuation. issufiiciently rapid. i

Trailer units can be cut outrbylopening th'e During each sanding operation lithesand boss? is sealed from themeasuringtcham bars l5, 76, the local chambers 9i are-sealed from the corresponding traps 68, and thenozzles h8fil areactive to deliver measuredichargesof sand fromthe: respective measuringachambers to; the

local. Chambers 9!. Timedoperation of jets. I08.

andv H idischarges .all.'sand"from the respective sand traps through the corresponding.nozzles! l 3, so that thesand traps empty. Atthe same time measured charges of sand are transferred from the measuring chambers l5, Hi'to the corresponding local chambers 9|.

At the termination of the sanding operation-the supply of air to the pipes 65, 66, B511 and 6611 will be'simultaneously terminated; The'pressure in these pipes will" be immediately dissipatedby' flow through the nozzles 66, I08 and H4; Conse quently, the valve I01 willopen deliveringthe accumulated charges from 'the local chambers to the corresponding sand "trapsfand:thevalve 84' will open permitting new charges to flow from" the main sand boxand fill the measuring-charm ber. i I

, In-this'way; and within-a few'seconds ofithe termination of sanding; the system'fis recharged" with sand for another timed sanding "operation:

The rubber nozzles I I3 are distensibleto 'free' ice and mud under the shock discharge-of the initial clean-out blast, but this ie'atureis a part of the subject matter-of the prior application above identified and is not here claimed.

Ashas already'been explained,' the embodiment ing-g a local chamber adjacent 2 the sand-- trap;

adapted to-a'ccumulatea charge of sand sumcient for one sandingoperation; pneumaticn means for transferring sand from: said source =-to' sander to sandand to cause said transferring means to operate simultaneously; and means rendered eifective by the termination of operation "of the last named means to cause delivery of sand from-said local chamber to said sand trap. 2. The combination of a sand trap ofthe pneumatic jet type located adjacent the point of sanding and adapted to retain when inactive a.

charge of sand for a single sanding operation; a

source of sand located at apoint relatively re+ mote fromthe point of sanding; a local cham-.

ber adjacent the sand trap, adapted to accumu late a charge of sand'suillcientfor a single-sanding operation; pneumatic means for transfer-- ring sandfrom said source to said chamber; means operable to-supply air under pressure simultaneously to the jets of said trap and to said transferring means to cause the trap to sand and cause transfer of'sand to said local cham-- ber; and means rendered effective by termination of said supply of air to deliver sand from said the point of sanding; a local chamber adjacent said sand trap and adapted to accumulate a charge of sand sufficient for a single sanding operation; normally open intercepting valve means between said chamber and trap and adapted to be closed when subjected to pneumatic pressure; pneumatic conveying means for transferring sand from said source to said chamber; and means operable to supply air under pressure simultaneously to said intercepting valve, conveying'means and the jets of said sander, and alternatively to cut off such supply.

4. The combination of a sand trap having a chamber adapted to retain a charge of sand for one sanding, a crest over which the sand must rise to discharge and air jet meansto flow the sand over the crest and propel it to the point of sanding; a local storage chamber normally in alternatively to cut oil said supply, and cause the motor to be vented.

5. The combination of ,a sand trap of the pneumatic jet type located adjacent the point of sanding and adapted to retain a charge of sand for a single sanding operation, a local storage I chamber normally in communication with said trap and arranged to deliver sand to the trap by gravity flow, said local chamber being vented to atmosphere; a sand retaining filter mounted in said vent to prevent the vescape of sand; a freely outward opening valve'for resisting the entrance of waterinto said chamber; an interceptingmechanism adapted to seal the communication between the local'storage chamber and the sand trap and comprising a valve, pressure motor means for closing the valve and means for biasing the valve in an openingdirection; a source of sand; a pneumatic jet conveyor for feeding sand from'said source tosaid-fstora ge chamber;

and means for supplying air under pressure to the jets ofsaid'trap and conveyor and to the mo:v tor of said giinterceptingvalve, and alternativelyv to cut off said supply and cause the motor to bevented. l 1' -6. The combination of a sand trap ofthe pneumatic jet type located adjacent the pointof sanding and adapted to retain a charge of sand for a single sandingoperation; a localstorage chamber normally in communication with the chamber of'the trap and arranged to-deliver sand thereto by gravity flow, said chamber, being of generally circular configuration fwhen viewed from aboveand 'having at its top an air vent, surrounded by a depending skirt; an intercepting mechanism adaptedto seal the communication between said chamber: and trap comprising a valve, pressure motor-means for closing the valve, and means biasing the valve in an opening direction; a source of sand; a pneumatic jetcon veyor for feeding sand from said source to said storage chamber, the parts being so arranged that the sand enters the storage chamber tangentially and in a portion outside said depending skirt, whereby centrifugal separation of sand and air is aiforded; and means for supplying air under pressure to the jets of said trap and conveyor' and to the motor of said intercepting valve, and alternatively to cut off said supply and cause the motor to be vented. I

'7. In a pneumatic sanding system the combination of a source of air under pressure; operator-operated means for controlling the supply of .air from said source; a main source of sand; normally open pneumatically closed intercepting valve means for closing the discharge of sand from said source; at least one unit comprisinga chamber fed by flow past said intercepting valve means and adapted to "contain sand for at least one sanding operation, jet means for transferring sand from said chamher, a local chamber to which said jet means delivers, a sand trap adapted to contain a charge of sand for a single sanding operation arranged to be fed by said local chamber and including jet means for discharging sand from said trap to the point of use in the sanding operation, a normally open pneumatically closed intercepting valve means for isolating said sand trap from its local chamber; and connections whereby said operator-operated means admits .air under pressure simultaneously to both said intercepting valve means and to the jet means of said sand transferring means and of said sand trap, and alternatively vents the same.

8. The combination defined in claim 7 in which I the intercepting valves are of the poppet type and coast with resilient seats provided with distensible approach tubes whereby hermetic sealing is assured despite resistance offered to tight closure by are inactive, a measured charge of sand which the jets when activeprogressively discharge, the first of said storing means being arranged to be fed with sand by gravity flow from a source;

*means forming a local storage chamber to which the first conveyor delivers, said local chamber being arranged to feed. the storing means of the second conveyor-by; gravity-'fl0w'; means for sup plying-end "cutting off" air under pressure to the I jets*of?se;id conveyors; and means-rendered ac tive-as=anincident to the supply of air tothe'jets to' cuo off feed "to the storage means of the con pelling sand from said measuring chamber; a

local! storage chamber to which the-last named jet means delivers, said local chamber being arranged normally'to deliver its charge-0f send to said'tr'ap; means forsupplyingairunder pressure to said jet means; and means rendered'ective as an inci'dentto the supply of air to said'jet means i to is'olatesa-id measuring meansfrom'seid source g and saidstrap from said: storage chamber;

11.. The combinationnof 'faasand .tratp-rincludinma-sand propelling jetnozzleand. means forfirev; taming a supply-"offiseucl:adjacent; said nozzle. whereby sandingmillcommence and continuesat leastv for; a; limited .period .upon the supply? of pressure fiuidsto said nozzle and :will terminate at" least ash-Yearly 'as the termination. of 1 saidkifliiid supplyya sand :ieeden connected to feed'ito-said,

trap and; including: a t. jet nozzle and means. for

' retaining-a supply of sand. adjacent said nozzle whereby feeding: wilLcQmmence and continue-at lea-stufor ai-limited periodquponzsupply' of' prese: f

suite 'fluid to saidqnozzle and. terminate at least as earlyzasthe termination of saidv fluidc'supply; a source .of' sand connected tosupply, sanditosaid v feeder; andzlmeaqns forisupplyingrpressure; fluid tan-said nozzles; substantiallysimultaneously; and:

for terminating: said supply;

summers; CAL H313EfLlls v 1 

